Question: Multiply.
Solution: When a number is next to a variable, it means they are multiplied. So, $({-9}{n^9})({1}{n^3})$ is the same as $({-9})({n^9})({1})({n^3})$. Now we can rearrange the factors because multiplication is commutative (a fancy way of saying that the order in which we multiply things doesn't matter). ${(-9)(1)}{(n^9)(n^3)}$ Then simplify, and we're done! ${-9}{n^{12}}$